Make line chart transitions more configurable in the Chart Authoring library

Details

Description

Currently, the line chart implementation has only a single style of transition between data - a sliding "page browse" style suitable for historical data browsing, but not suitable for real-time data streaming such as that provided by the Nexus sensors.

This improvement will do the following:

1) Extract the existing transitioning logic for lines, areas and points to separate functions from the current update* functions.

2) Add a transition*-type invoker to allow an end user or implementing component to supply a different transition behaviour.

3) Provide some additional styles of transition, including one more suitable for real-time data.